Software loadable avionics units (i.e., line replaceable units or LRUs) have the capability of downloading stored information onto a diskette. Present maintenance practices call for transferring aircraft data stored on certain LRUs onto floppy disk media utilizing a portable or PC-based ARINC 615-3 data loader. To transfer the stored aircraft data, a properly configured 3¼″ floppy diskette is inserted into the data loader. In some cases, a permanently mounted airborne data loader may be used to perform this task for an aircraft installation. For example, on Boeing 737 aircraft, flight management computers (FMCs) are capable of downloading their stored faults onto floppy disks as described above. On Boeing 747 aircraft, a central maintenance computer is able to download its fault history database and an aircraft condition monitoring system (ACMS) is capable of downloading its stored serial stream aircraft parameters data, including up to eight selected channels of recorded smart access recorder data and triggered reports for the aircraft communications and reporting system (ACARS).
Two-way communication utilizing standard ARINC 615-3 protocol is needed for all LRUs that require periodic software updates. In at least one aircraft configuration, wires used for this communication are routed to a multiple deck rotary switch. The rotary switch is used by an operator to manually switch appropriate outputs from avionics boxes to an airborne data loader or to a connector for a portable data loader. The wiring passes from an electronics equipment (EE) bay to a centralized flight deck location. This configuration does not permit remote initiation of ARINC 615-3 communication because of the need for an operator to manually configure the communication path using the rotary switch. However, if such initiation were possible, a central maintenance function for the aircraft could be provided.